System and method for modifying talocalcaneal relationship in a foot

ABSTRACT

A system for modifying a talocalcaneal spatial relationship in a foot in a body, including a subtalar spacer having an articulating surface and implanted in the sinus tarsi of the foot and a fastener that fastens the subtalar spacer to a bone surface in the foot, in which the articulating surface of the subtalar spacer directs relative movement between the calcaneus and the talus of the foot.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/173,959, filed 29 Apr. 2009, which is incorporated in its entirety bythis reference.

TECHNICAL FIELD

This invention relates generally to the implant field, and morespecifically to an improved subtalar implant in the arthroereisis field.

BACKGROUND

Hyperpronation and flat feet (“fallen arches”) are relatively commonconditions of the feet that cause pain, such as during sports or dailyactivities like walking. These conditions can be caused by collapse thruthe sinus tarsi. The sinus tarsi is a space between the talus and thecalcaneus. It is funnel shaped with the larger opening on the lateralside of the foot progressing across the foot to end in a small medialopening between the two aforementioned bones. This lateral opening orspace between the bones is normally maintained by the tension ofligaments located on the medial side of the talus and the posterior sideof the calcaneus. When these ligaments fail due to either injury ordisease, the talus is allowed to sublux or deviate from its normalposition atop the calcaneus. This subluxation shifts the location of thecalcaneus laterally (causing flatfoot), and allows the arch of the footto collapse, increasing pronation. When this happens, the funnel shapedlateral opening of the sinus tarsi disappears.

Common noninvasive treatments for hyperpronation and flat feet includethe use of foot orthotics and shoe modifications. Situations in whichthese treatments fail to relieve symptoms may require implantation of asubtalar arthroereisis, a type of “bone block”, in the sinus tarsi to“reopen” the collapsed sinus tarsi. The subtalar arthroereisis typicallyacts as a spacer to limit motion of the talus. However, afterimplantation of current subtalar arthroereisis systems, thearthroereisis often become loose within the sinus tarsi, causing painfulirritation of the surrounding tissue. Furthermore, these systems are notstable enough to accurately reconstitute the anatomy of the sinus tarsi.Once the system fails, removal is mandatory, with resultant painfulcollapse and the need for a formal subtalar arthrodesis (joint fusion).

Thus, there is a need in the implant field to create an improvedsubtalar arthroereisis. This invention provides such an improvedsubtalar arthroreisis.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are a perspective view and a side view, respectively, ofa first variation of the spacer body portion of the subtalar spacer ofthe first preferred embodiment of the system;

FIG. 1C is a perspective view of a first variation of the spacer mountportion and the fastener of the first preferred embodiment of thesystem;

FIG. 1D is an anterior-lateral view of a variation of the firstpreferred embodiment of the system assembled and implanted in the sinustarsi;

FIG. 2A is a perspective view of a second variation of the spacer mountportion and the fastener of the first preferred embodiment of thesystem;

FIGS. 2B and 2C are perspective views of a second variation of thespacer body portion of the subtalar spacer of the first preferredembodiment of the system;

FIG. 2D is an anterior-lateral view of a variation of the firstpreferred embodiment of the system assembled and implanted in the sinustarsi;

FIGS. 3A and 3B are perspective views of another version of the secondvariations of the spacer mount portion and the spacer body portion,respectively, of the subtalar spacer of the first preferred embodimentof the system;

FIG. 3C is an anterior-lateral view of a variation of the firstpreferred embodiment of the system assembled and implanted in the sinustarsi;

FIGS. 4A and 4B are perspective and side views, respectively, of thesubtalar spacer and fastener of an alternative embodiment of the system;

FIG. 4C is an anterior-lateral view of an alternative embodiment of thesystem implanted in the sinus tarsi;

FIGS. 5A and 5B are perspective and side views, respectively, of thesubtalar spacer and fastener of an alternative embodiment of the system;

FIG. 5C is an anterior-lateral view of an alternative embodiment of thesystem implanted in the sinus tarsi;

FIG. 6A is a side view of the subtalar spacer and fastener of the analternative embodiment of the system;

FIG. 6B is an anterior-lateral view of an alternative embodiment of thesystem implanted in the sinus tarsi;

FIGS. 7A through 7D are perspective views of a first spacer mountportion, first spacer body portion, second spacer mount portion, andsecond body portion, respectively, of an exemplary second preferredembodiment of the system;

FIG. 7E is an anterior-lateral view of the first and second subtalarspacers of an exemplary second preferred embodiment of the systemimplanted in the sinus tarsi; and

FIG. 8 is a schematic of an embodiment of the method for modifyingtalocalcaneal relationship in a foot.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of preferred embodiments of the invention isnot intended to limit the invention to these preferred embodiments, butrather to enable any person skilled in the art to make and use thisinvention.

As shown in FIGS. 1 through 7 , the system 100 for modifying atalocalcaneal spatial relationship of the preferred embodiment includesa subtalar spacer 110 having an articulating surface 112, and a fastener140 that fixes the subtalar spacer 110 to a bone surface in the foot, inwhich the articulating surface 112 of the subtalar spacer 110 directsrelative movement between the calcaneus and the talus of the foot. Thesystem 100 preferably restores a normal talocalcaneal spatialrelationship by restoring the sinus tarsi in the foot and directing thecompressive and sliding forces generated between the talus and calcaneusas the talus moves over the calcaneus during daily activities. Thesliding motion creates a movable yet stable joint for reducingconditions caused by a collapsed sinus tarsi, including hyperpronationof the foot and flat feet.

The subtalar spacer 110 of the system 100 functions to restore the sinustarsi space in a foot of a body. The subtalar spacer 110 is preferablyimplanted in the sinus tarsi of the foot and elevates (when the body isin a standing position) the talus bone relative to the calcaneus bone ofthe foot. The subtalar spacer 110 preferably includes an articulatingsurface 112, a spacer body portion 120, and a spacer mount portion 130.

The articulating surface 112 of the subtalar spacer 110 is preferably asurface on the spacer body portion 120 or any suitable portion of thesubtalar spacer 110 that functions to direct forces between the talusand calcaneus as the talus moves over the calcaneus during dailyactivities. The articulating surface 112 preferably provides a surfacefor a bone, another spacer body portion, and/or any suitable tissue orsurface to contact the subtalar spacer no. As shown in FIGS. 1 through 7, the articulating surface 112 is preferably generally smooth tofacilitate a sliding motion on the articulating surface 112, but may beribbed, grooved, and/or have any suitable texture for articulating withanother surface in any suitable articulating motion such a rollingand/or rubbing.

The spacer body portion 120 of the subtalar spacer no functions toprovide structural support for the restoration of the sinus tarsi. Thespacer body portion 120 may be one of several variations. In a firstvariation, as shown in FIGS. 1A through 1D, the spacer body portion 120is adapted to be fixed to the calcaneus bone. As shown in FIGS. 1A and1B, the spacer body portion 120 is preferably shaped to fill asignificant portion of the sinus tarsi, and the articulating surface 112is preferably contoured to articulate with an inferior surface of thetalus bone. In particular, as shown in FIG. 1E, the articulating surface112 is preferably on the superior side of the spacer body portion 120and is gently sloped to articulate in a sliding motion with the anteriorand/or lateral aspects of the inferior surface of the talus bone, butthe articulating surface 112 may alternatively articulate with anysuitable surface in any suitable motion. In a second variation, as shownin FIGS. 2A through 2D, the spacer body portion 120′ is adapted to befixed to the talus bone. As shown in FIGS. 2B and 2C, the spacer bodyportion is preferably shaped to fill a significant portion of the sinustarsi, and the articulating surface 112 is preferably contoured toarticulate with a superior surface of the calcaneus bone. In particular,as shown in FIG. 2D, the articulating surface 112 is preferably on theinferior side of the spacer body portion 120′ and is sloped andcontoured in a convex manner to articulate with a portion of thesuperior surface of the calcaneus bone in a sliding motion.Alternatively, as shown in FIGS. 3B and 3C, the articulating surface 112on the spacer body portion 120″ may be sloped and contoured in a concavemanner to complement another portion of the superior surface of thecalcaneus bone. However, the articulating surface 112 may articulatewith any suitable surface in any suitable motion.

The spacer mount portion 130 of the subtalar spacer no functions toprovide a surface for the fastener 140 to fasten the subtalar spacer noto a surface. By fastening the subtalar spacer no to a surface, thespacer mount portion 130 fixes the subtalar spacer 110 within the sinustarsi, helping to promote bony ingrowth into the implant that reducesthe likelihood of the subtalar spacer 110 loosening within the sinustarsi and reduces pain. The spacer mount portion 130 may be one ofseveral variations. In a first variation, as shown in FIGS. 1C and 1D,the spacer mount portion 130 is adapted to attach to the calcaneus bone.The inferior side of the spacer mount portion 130 preferably includes agenerally flat planar surface for the fastener 140, which increasesstability of the subtalar spacer 110 on the bone and simplifies surgicalpreparation for the implantation of the subtalar spacer no. However, theinferior side of the spacer mount portion 130 may alternatively becurved, sloped, complementary to the natural contours of the calcaneus,a custom surgically prepared surface, or any suitable geometry. In asecond variation, as shown in FIGS. 2A and 2D, the spacer mount portionis adapted to attach to the talus bone. The superior side of the spacermount portion 130′ is preferably similar to the inferior side of thespacer mount of the first variation, except that the superior side ofthe spacer mount portion of the second variation may be curved, sloped,complementary to the natural contours of the talus, or any suitablegeometry. As shown in FIGS. 3A and 3C, the spacer mount portion 130″ ofthe second variation may alternatively include a branch that has a firstend 132 and a second end 134 that are adapted to attach to the talusbone. As shown in FIG. 3C, the multiple ends of the branch preferablyprovide additional mounting areas to improve fixation of the subtalarspacer 110 to the surface, and facilitate proper positioning of thealternative spacer body portion of the second variation to articulatewith the calcaneus bone. The first end 132 is preferably a lateral endthat is adapted to attach to a lateral portion of the inferior side ofthe talus, and the second end 134 is preferably a medial end that isadapted to attach to a medial portion of the anterior/inferior side ofthe talus. However, the first and second ends of the branch mayalternatively be adapted to attach to any suitable portions of the talusand/or any suitable surface. Alternatively, the branch may include morethan two ends, each of which is adapted to attach to a suitableindividual portion of the talus or any other suitable surface.

The spacer body portion 120 and the spacer mount portion 130 arepreferably separate components and the spacer body portion 120 ispreferably coupled to the spacer mount portion 130. As shown in FIGS. 1through 3 , the spacer body portion 120 preferably includes a boss 122and the spacer mount portion 130 preferably includes a recess 136, suchthat the boss 122 of the spacer body portion 120 couples to the recess136 of the spacer mount portion 130. The boss of the spacer body portion120 may have footprint of a square shape 122 as shown in FIG. 1B, arectangular shape 122′ as shown in FIG. 2C, a cross shape 122″ as shownin FIG. 3B, circular, any suitable polygon, and/or any suitable shape.Alternatively, the spacer body portion may include a plurality ofbosses. The spacer body portion 120 may include a key and the spacermount portion 130 may include a keyway such that the spacer body portionand the spacer mount portion are restrained to couple in one orientationto help prevent accidental reversal or undesired orientations of thespacer body portion relative to the spacer mount portion. The spacerbody portion 120 preferably couples to the spacer mount portion 130 in apermanent fashion, but may alternatively be semi-permanent and/orselectively removable to facilitate applications such as adapting to agrowing and changing skeletal frame such as in a child, and obtaining atrial-and-error custom fit. The spacer body portion 120 preferablycouples to the spacer mount portion 130 with a press-fit, but mayalternatively and/or additionally couple to the spacer mount portionwith cement, screws, bolts, and/or any suitable adhesive or fastener.

The spacer body portion 120 is preferably made of a durable,shock-absorbent and biocompatible material such as ultra high molecularweight polyethylene, but may alternatively and/or additionally be madeof any suitable material. The spacer body portion is preferably made inan injection molding process, but may alternatively be made by milling,3D printing, or any suitable manufacturing process. The spacer mountportion 130 is preferably made of a durable, biocompatible material suchas titanium, but may alternatively and/or additionally be made of anysuitable material. The spacer mount portion is preferably made in acasting or molding process, but may alternatively be made by milling orany suitable manufacturing process.

The subtalar spacer 110 may alternatively include multiple spacer bodyportions 120. As an example, the subtalar spacer no may include multiplespacer body portions 120 that couple to each other and/or to the spacermount portion, in a puzzle-like fashion, and/or in a manner similar tothat described above. Multiple spacer body portions 120 may be usefulfor some situations, such as swapping individual spacer body portions toobtain a custom fit.

In other alternatives, as shown in FIGS. 4 through 6 , the spacer bodyportion 120 and the spacer mount portion 130 may alternatively beintegrated into a single component. In these alternatives, thegeometries of the spacer body portions and spacer mount portions aresimilar to those described above and shown in FIGS. 1 through 3 . Inparticular, the subtalar spacer with integrated spacer body portion 120and spacer mount portion 130 may be designed to be fixed to thecalcaneus (FIG. 4 ), or to the talus (FIGS. 5 and 6 ).

The fastener 140 of the system 100 functions to fasten the subtalarspacer 110 to a bone surface in the foot. In particular, the fastener140 preferably fastens the subtalar spacer 110 to the calcaneus bone orthe talus bone. The fastener 140 may, however, fasten the subtalarspacer 110 to any suitable surface. The fastener 140 is preferablyintegrated into the spacer mount portion of the subtalar spacer 110, butmay alternatively be a separate component and coupled to the spacermount portion 130. The fastener 140 preferably fastens the subtalarspacer 110 to a bone surface by being inserted into the bone andpromoting bony ingrowth into the system. The fastener 140 is preferablya protrusion in the shape of a peg 140′ (as shown in FIGS. 1C and 3A), atab 140″ (as shown in FIG. 1C), a keel 140′ (as shown in FIG. 2A),and/or any suitable shape. However, the fastener 140 may alternativelyand/or additionally include bone cement, screws, bolts, and/or anysuitable adhesive or fastener. As shown in FIGS. 1C, 2A, and 3A, thefastener preferably includes a plurality of these structures, to anchorthe subtalar spacer 110 to the bone. The fastener 140 may furtherinclude threads, bumps, notches, and/or any suitable texture toencourage bone growth for tissue fixation of the fastener within thebone, and may alternatively and/or additionally include bone growthfactors to enhance bone growth. The fastener 140 is preferably insertedinto the bone after the bone is surgically prepared, such as by levelingand/or drilling holes into the bone.

The fastener 140 is preferably made of a biocompatible material andthrough a manufacturing process similar to that of the spacer mountportion 130 of the subtalar spacer 110.

In a second preferred embodiment, as shown in FIGS. 7A through 7E, thesystem 200 includes a first subtalar spacer 210, a first fastener 240, asecond subtalar spacer 250 and a second fastener 280. The first fastener240 and second fastener 280 are preferably identical to the fastener 140of the first preferred embodiment of the system 100. The first subtalarspacer 210 (which includes a first spacer body portion 220 and a firstspacer mount portion 230) and second subtalar spacer 250 (which includesa second spacer body portion 260 and a second spacer mount portion 280)are preferably similar to the subtalar spacer 110 of the first preferredembodiment of the system 100, except as described below. As shown inFIG. 7E, the second subtalar spacer 250 is preferably adapted to beimplanted in the sinus tarsi directly opposite the first subtalar spacer210. The spacer body portions 220 and 260 of the first and secondsubtalar spacers, respectively, preferably are generally complementaryand fill a significant portion of the sinus tarsi when implanted. Thearticulating surface 212 of the first subtalar spacer 210 preferablyarticulates with the articulating surface 252 of the second subtalarspacer 250. In the embodiment as shown in FIG. 7E, the articulatingsurfaces of the first and second subtalar spacers are preferablycomplementary to each other, such that the articulating surfaces 212 and252 of the first and second subtalar spacers, respectively, articulatewith each other in a sliding motion. However, the articulating surfacesof the first and second subtalar spacers may alternatively articulatewith each other in a rolling, rubbing, or any suitable articulatingmotion. For example, as shown in FIG. 7E, a first subtalar spacer 210may be implanted in the talus bone and a second subtalar spacer 250 maybe implanted in the calcaneus bone, such that the articulating surface212 of the first subtalar spacer 210 contacts the articulating surface252 of the second subtalar spacer in a sliding manner. In this example,the articulating surfaces of the first and second subtalar spacers aremade of ultra high molecular weight polyethylene forpolyethylene-polyethylene articulating contact, which reduces thetendency of painful loosening of the first and second subtalar spacers.However, the articulating surfaces of the first and second subtalarspacers may alternatively be made of any suitable material, and becontoured in any suitable manner for articulation with each other.

As shown in FIG. 8 , a method 300 for modifying a talocalcaneal spatialrelationship in a foot in a body includes the steps of providing a firstsubtalar spacer having an articulating surface S310, providing a firstfastener that fastens the subtalar spacer to a surface in the foot S320,implanting the first subtalar spacer in the sinus tarsi of the footS330, and allowing the articulating surface of the first subtalar spacerto direct relative movement between the calcaneus and the talus of thefoot S34 o. The method preferably restores a normal talocalcanealspatial relationship by restoring the sinus tarsi in the foot, therebyreducing conditions caused by a collapsed sinus tarsi, includinghyperpronation and flat feet.

The step of implanting the first subtalar spacer in the sinus tarsi ofthe foot S330 preferably includes preparing a surface and inserting thefastener into the bone surface. The surface is preferably on thecalcaneus bone or the talus bone, but may alternatively be any suitablebone or any suitable surface. Preparing the surface is preferablysimilar to typical conventional preparation for surgical implantationsand may include drilling, sanding, and/or other manipulations of thebone that are known to one ordinarily skilled in the art. Inserting thefastener into the bone surface preferably includes inserting a peg, tab,keel, or any suitable portion of the fastener into the bone surface.Alternatively, the step of implanting the first subtalar spacer in thesinus tarsi of the foot may include applying cement, or utilizingscrews, bolts, and/or any suitable adhesive or fastener.

In one variation of the method, the step of allowing the articulatingsurface of the first subtalar spacer to direct relative movement betweenthe calcaneus and the talus of the foot S340 preferably includes thestep of allowing the articulating surface of the first subtalar spacerto articulate with a surface of the calcaneus. The articulation betweenthe first subtalar spacer and the calcaneus is preferably a slidingmotion, but may additionally and/or alternatively be a rolling, rubbing,and/or any suitable articulation. The sliding motion preferably helpsdirect forces between the talus and calcaneus as the talus moves overthe calcaneus during daily activities, creating a movable yet stablejoint. In this variation, the step of providing a fastener that fastenspreferably includes providing a fastener that fastens the first subtalarspacer to the talus.

In another variation of the method, the step of allowing thearticulating surface of the first subtalar spacer to direct relativemovement between the calcaneus and the talus of the foot S340 preferablyincludes the step of allowing the articulating surface of the firstsubtalar spacer to articulate with a surface of the talus. Thearticulation between the first subtalar spacer and the calcaneus ispreferably a sliding motion, but may additionally and/or alternativelybe a rolling, rubbing, and/or any suitable articulation. The slidingmotion preferably helps direct forces between the talus and calcaneus asthe talus moves over the calcaneus during daily activities, creating amovable yet stable joint. In this variation, the step of providing afastener that fastens preferably includes providing a fastener thatfastens the first subtalar spacer to the calcaneus.

In another embodiment of the method, the method 300 preferably furtherincludes the steps of providing a second subtalar spacer having anarticulating surface S350, providing a second fastener that fastens thesecond subtalar spacer to a surface in the foot S360, and implanting thesecond subtalar spacer in the sinus tarsi of the foot S37 o. In thisembodiment, the step of allowing the articulating surface of the firstsubtalar spacer to direct relative movement between the calcaneus andthe talus of the foot S340 preferably includes allowing the articulatingsurface of the first subtalar spacer to articulate with the articulatingsurface of the second subtalar spacer.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

1-21. (canceled)
 22. An apparatus, comprising: a spacer configured to beimplanted in a foot, the spacer including: a spacer body including anengagement surface contoured to engage with at least one of a talus bonein the foot or a calcaneus bone in the foot; and a spacer mount coupledto the spacer body and including a first spacer mount portion sized toengage the talus bone or the calcaneus bone.
 23. The apparatus of claim22, wherein the engagement surface is smooth.
 24. The apparatus of claim22, wherein the engagement surface is at least one of ribbed or grooved.25. The apparatus of claim 22, wherein the first spacer mount portion islocated proximate a superior side of the spacer mount, the superior sidehaving a geometry that is at least one of curved, sloped, orcomplementary to natural contours of the talus bone.
 26. The apparatusof claim 22, wherein the spacer mount includes a branch having a firstend and a second end that are both configured to attach to the other ofthe talus bone or the calcaneus bone.
 27. The apparatus of claim 22,wherein the spacer body is configured to be removably coupled to thespacer mount.
 28. The apparatus of claim 27, wherein the spacer bodyincludes a boss and the spacer mount includes a recess such that theboss of the spacer body is configured to couple to the recess of thespacer mount.
 29. The apparatus of claim 22, wherein the spacer body ismade of a biocompatible material.
 30. The apparatus of claim 22, furthercomprising a fastener removably coupled to the spacer mount.
 31. Theapparatus of claim 30, wherein the fastener is configured to promotebony ingrowth into the apparatus.
 32. The apparatus of claim 30, whereinthe spacer mount is configured to attach to the calcaneus bone and aninferior side of the spacer mount includes a flat planar surface of thefastener.
 33. The apparatus of claim 22, wherein the spacer body isintegral to the spacer mount.
 34. The apparatus of claim 22, wherein thespacer mount includes one or more features to promote bony ingrowth intothe apparatus.
 35. The apparatus of claim 30, wherein the fastenerincludes at least one of a peg, a tab, or a keel.
 36. The apparatus ofclaim 22, wherein the first spacer mount portion of the spacer mount isat least one of curved, sloped, or complementary to natural contours ofthe calcaneus bone.
 37. An apparatus, comprising: a first spacerconfigured to be implanted in a foot, the first spacer including a firstspacer body and a first spacer mount coupled to the first spacer body,the first spacer body including a first engagement surface, a first basesurface, and an outer surface extending from the first engagementsurface to the first base surface; and a second spacer configured to beimplanted in the foot, the second spacer including a second spacer bodyand a second spacer mount, the second spacer body including a secondengagement surface, the first engagement surface is configured to engagewith the second engagement surface to direct relative movement between afirst bone in the foot and a second bone of the foot.
 38. The apparatusof claim 37, wherein at least a first portion of the first engagementsurface is one of convex or concave, and at least a second portion ofthe second engagement surface is the other of convex or concave to becomplementary to the first portion of the first engagement surface. 39.The apparatus of claim 38, wherein the first spacer and the secondspacer are made of polyethylene.
 40. The apparatus of claim 39, whereinthe second spacer is configured to be implanted in a sinus tarsi of thefoot directly opposite the first spacer.
 41. The apparatus of claim 37,wherein the first spacer is configured to engage in one of a sliding,rolling, or rubbing motion with respect to the second spacer.
 42. Theapparatus of claim 37, wherein the first spacer mount includes one ormore features to promote bony ingrowth into the apparatus.